1. Field of the Invention
The present invention relates to a latching apparatus for safety bindings used for binding ski boots to skis and more particularly for bindings which may be activated multidirectionally.
2. Description of Prior Art
Numerous devices have been proposed for securing boots to skis in order to increase the safety of the skier in the event of a fall. These devices result in automatic release under the effect of a force exceeding a certain threshold in the vertical direction (frontward fall) or in the lateral direction such as occurs when the foot is twisted. Often the latching elements provided to respond to each of these forces are distinct from one another and function independently depending upon the type and direction of force exerted. The use of separate devices makes it difficult, if not impossible, to respond to forces of different types which are exerted in combination, as often occurs.
Furthermore, although latching devices which function independently of the type of force exerted, i.e., of one type or another, have been developed but also suffer from the above disadvantage.
Another problem occurs by virtue of the fact that the leg of the skier reacts mechanically in a different fashion to a flexion force such as occurs in a frontwards fall than to a torsional or twisting force caused by a lateral force or twist. The safety threshold is thus different in the two cases and this difference must be taken into account to avoid premature release without nevertheless reducing the safety of the binding in the case of a strong force. Thus, it is accepted that a ratio of 2:1 between the vertical release force and the lateral release threshold force results in a definite improvement and tests have even shown that it is preferable to attempt to achieve a ratio of 4:1.
French Pat. No. 1,045,717 proposes a device which attempts to partially resolve the problems referred to above. The device comprises a latching finger whose one end cooperates with a seating integral with the ski boot or shoe. This finger can, as a result of the force transmitted by the shoe, pivot against the return force of an adjustable spring in an opening provided in the wall of a casing integral with the ski. At a given rocking amplitude the finger leaves the seating which in turn frees the boot. A release threshold is achieved in this device by means of a rectangular base integral with the finger and rests in a locking fashion along one of its sides on the internal surface of the wall of the container. One thus obtains for the action of the spring a lever arm which is greater in cases of vertical release wherein a small side of the rectangle serves as the pivoting axis as opposed to lateral release wherein the large side of the rectangle comes into play. Although this device constitutes an improvement, it is entirely inadequate to respond to a combined force having vertical and horizontal components.
French Pat. No. 1,554,728 attempts to provide a device which responds to this type of combined force. The device is similar to the one discussed, however the base of the finger resting on the internal surface of the container is generally cylindrical. The force exerted against the return spring results in a rocking or pivoting whose amplitude is independent of the direction of the force exerted by the boot on the finger because the lever arm is independent of this direction. The safety device, therefore, responds to any force, whatever the direction, but makes it impossible to resolve the problem of obtaining a greater than 1:1 ratio as between the vertical and lateral release thresholds. To obtain a ratio approaching 2:1 is however possible by a modification which comprises fixing the boot to the ski by two identical devices. One of the devices cooperates with the front of the boot while the other cooperates with the heel of the boot. This arrangement increases the complexity of the assembly and renders adjustment of the assembly delicate.